American grapes are usually grown on tensioned wire trellises. The wire trellises, in accordance with the prior art practice, are placed under high tension and supported on wooden cross-arms which, in turn, are nailed to the upper ends of wooden stakes. The stakes are driven into the ground, and are positioned in rows. The tensioned trellis wires are stapled to the ends of the cross-arms and extend along each row of the vineyard to provide trellises for the vines.
Copending application Ser. No. 202,784 filed Oct. 31, 1980 in the name of the present inventor, now abandoned, seeks to overcome some of the problems encountered by the use of wooden stakes and wooden cross-arms, and provides cross-arms formed of metal, such as galvanized iron, which are mounted on wooden stakes while the stakes are upright in the ground. The ends of the metal cross-arms in the assembly described in the copending application are slotted to receive the tensioned trellis wires, so that no stapling of the trellis wires to the cross-arms is required, as is the case with the wooden cross-arms.
U.S. Pat. No. 4,329,811, which issued May 18, 1982, in the name of the present inventor, discloses an all-metal grape stake which includes a metal upright member and which also includes a cross-arm in the form of a metal strip which is attached to and extends across the upper end of the upright member. The ends of the cross-arm likewise are slotted to receive the tensioned trellis wires in a sliding relationship.
Problems have arisen with respect to the metal cross-arms such as are used in the two assemblies discussed above, in that the cross-arms are slidable along the tensioned trellis wires. This means that any irregularities in the vine load on the individual cross-arms have a tendency to cause the arms to turn and collapse, because the hat section which connects the cross-arm to the top of the stake has little resistance to torque and buckles in the presence of angular movement. The collapse of any one of the cross-arms creates a domino effect, since it loads the adjacent cross-arms causing them also to collapse, and so on.
In the embodiment of the invention to be described, means in the form of clips are provided which are mounted over the ends of the cross-arms and which have slotted sides which bite into the tensioned trellis wires to inhibit sliding movement of the ends of the cross-arms along the trellis wires. This causes the trellis wires themselves to contribute to the integrity of the overall assembly, and to obviate any tendency for the cross-arms to slide along the trellis wires and collapse.
In the usual installation the trellis wires are formed, for example, of high tensile galvanized steel, and they are placed under a tension of the order of 200,000 psi. The clips used in the assembly of the present invention may be formed of heat-treated spring steel.
The combination of the clips and the trellis wires in conjunction with the cross-arms and upright stakes provide a strong trellis assembly in which there is no tendency for the cross-arms to turn and collapse even in the presence of high off-balance loads of the vines.
A feature of the invention is that existing trellis assemblies using metal cross-arms may be easily retrofitted to incorporate the teachings of the invention, by driving clips of the type to be described over the slotted ends of the cross-arms and into engagement with the tensioned trellis wires to inhibit any sliding movement of the cross-arms along the wires. The only tool required for this operation is a hammer.